Bitcoin soared to the highest level in a year, extending a run that's seen prices more than double since March. The largest cryptocurrency climbed as much as 10% Monday from levels late Friday, and was trading at $8,847 as of 10:25 a.m. in Tokyo. Rival coins were also stronger at the start of the week. Litecoin added almost 9% and Ether, the second largest digital token, rose 6%.